Storage systems using a solid state drive (SSD) and a hard disk drive (HDD) in combination as an auxiliary storage, for example, increase processing performance by effectively using the SSD with a low latency and achieve cost reduction by using an inexpensive HDD to secure a large capacity.
In such a storage system, storage hierarchy control is often performed. For example, in a lower layer, a pool for the SSD and a pool for the HDD are managed, while in an upper layer, an overall logical storage area is controlled. The storage hierarchy control improves the performance appropriately by allocating data with a high access frequency to the SSD.
In related art, it is attempted to improve the processing performance of the storage hierarchy control by predicting a range to be accessed. For example, preloading based on static patterns of pieces of data that have accessed at the same time is proposed.
Examples of the related art include Japanese Laid-open Patent Publication Nos. 2015-219926, 2006-260067, and 2003-167781.